1. Field of the Invention
This invention broadly relates to components used in the course of orthodontic therapy. More particularly, the present invention relates to an assembly of an orthodontic band and orthodontic appliance, as well as a method of making the same.
2. Description of the Related Art
Orthodontic treatment is a specialized area within the general field of dentistry. Orthodontic treatment involves movement of crooked or misaligned teeth to preferred locations and orientations along the dental arch. At the conclusion of treatment, the aesthetic appearance of the patient's oral structure is often greatly improved and in many instances the patient's occlusion, or function of the teeth during eating, is enhanced.
One type of orthodontic treatment involves the use of a set of components that are commonly known collectively as “braces”. These components include a set of small slotted devices known as brackets that are secured to the patient's anterior, cuspid and bicuspid teeth. An archwire is held in the slots of the brackets and functions as a track to guide movement of the teeth to orthodontically correct positions. The teeth are often moved by bends or twists placed in the archwire or by elastic members connected to one or more of the brackets.
Oftentimes, small devices known as buccal tubes are secured to the molar teeth. The buccal tubes have elongated enclosed passageways that receive ends of the archwires. Some buccal tubes have “convertible” passageways that can be opened along one side in order to convert the appliance into a slotted bracket when desired.
In past years, it was common practice to weld each buccal tube and bracket to a corresponding orthodontic band. The orthodontic bands were selected to match the contour and circumferential dimensions of the tooth so that a close, non-loosening fit between the band and the tooth could be achieved. In more recent years, however, adhesives have been developed that have sufficient strength to affix brackets and buccal tubes directly to the surfaces of the tooth without the need for a band.
However, buccal tubes are often subjected to relatively large forces from occluding teeth as well as forces exerted by the archwire. In addition, molar teeth have relatively large roots and are sometimes used as an anchoring location for resisting forces imposed by orthodontic components that are connected to other teeth in the oral cavity. As a result, many practitioners prefer to continue to use buccal tubes that are connected to an orthodontic band so that a stable support platform for the buccal tube is provided.
Welded bracket and band assemblies are also still used in certain instances with anterior, cuspid and bicuspid teeth. For example, in some cases a relatively strong connection to a tooth is desired and the use of a band ensures that the bracket will remain securely coupled to the associated tooth. In other instances, the patient may have a weak or fractured tooth or a tooth restoration that may preclude the bonding of a bracket directly to a tooth with sufficient strength to safely resist the expected forces that may be encountered during the course of treatment.
Other orthodontic appliances may also be connected to bands instead of brackets or buccal tubes. Examples of such other appliances include cleats, buttons, hooks, lingual sheaths and eyelets. The appliances may be mounted either on the buccolabial side of the band (i.e., the side facing the patient's cheeks or lips) or on the lingual side of the band (i.e., the side facing the tongue of the patient).
Typically, orthodontic bands and the appliances that are connected to bands are made of a metallic material such as stainless steel. These assemblies are often connected together by a brazing or welding process. An improved process for welding appliances to bands is described in applicant's U.S. Pat. No. 5,529,491.
The shape of orthodontic bands is generally considered complex. Many orthodontic bands are provided with rounded protrusions that extend inwardly toward the middle of the band. These protrusions are adapted to fit within small recesses of a patient's tooth, such as the concave regions between adjacent cusps of a patient's molar tooth. Protrusions help to mechanically interconnect the band to the tooth and reduce the likelihood that the band will shift or rock during the course of treatment. In addition, the use of protrusions that match the shape of recesses in a patient's tooth can avoid undue gaps between the band and underlying areas of the tooth that might otherwise trap food and promote tooth decay.
Moreover, one or both edges of the band may extend along an undulating path that does not lie in a flat reference plane. For example, the gingival perimeter (i.e., the perimeter facing the patient's gingiva or gums) may extend outwardly in a gingival direction along a curved path in areas next to the buccolabial side of the patient's tooth and the lingual side of the tooth. In those areas, the gingiva is normally located a relatively large distance from the outer tip of the tooth. However, in areas adjacent the mesial side of the tooth (i.e., the side of the tooth facing the middle of the patient's dental arch) and the distal side of the tooth (i.e., the side of the tooth facing away from the middle of the patient's dental arch) the perimeter of the band may curve in an occlusal direction. In those areas, the gingiva is typically located closer to the outer tip of the tooth. Such construction helps to avoid contact of the band with the patient's gingival and yet provides good resistance to lateral movement or rocking during use.
Similarly, the occlusal edge of the band may curve in an occlusal or gingival direction in different regions along its perimeter. For example, the occlusal edge may curve in a gingival direction in order to avoid extending past the tooth in an occlusal direction, particularly in areas between the cusps of molar teeth as described above.
The position of the appliance on the band is an important consideration during treatment. For example, if the band is not placed in a correct location along a mesial-distal reference axis, the archwire may cause the tooth to be rotated about its long axis to an undesirable orientation. Similarly, if the appliance is not placed on the band in a correct location with respect to an occlusal-gingival reference axis, the archwire may cause the tooth to be moved to an unsatisfactory location in an occlusal or gingival direction. For these reasons, orthodontic practitioners are often careful to specify the exact position of the appliance on the band for each patient, depending on the treatment at hand.
However, it has been a cumbersome procedure in the past for manufacturers to ensure that appliances were positioned on the bands at precise, correct locations. In some cases, the band was placed in a first jig having a shape that matched the shape of the band, including protrusions formed in the band. A second jig was also provided to hold the appliance and orient the appliance to the desired location on the band.
Unfortunately, the protrusions described above do not provide a precise, consistent means of orienting the band to the jigs. The protrusions are typically smoothly curved and the center of the curve may be difficult to ascertain. As a consequence, the accuracy of placement of the appliance on the band is impaired.
Consequently, in the past it has been common practice to visually inspect each band at close range by an inspector in the manufacturer's facility using a toolmaker's eye scope or video camera. Visual inspection is used initially to ensure proper orientation of the appliance to the band before the appliance and the band are welded together. The visual inspection can also be used subsequent to the welding process to ensure that the appliance and band are correctly oriented relative to each other after assembly.
As can be appreciated, manual inspection by eye is somewhat time-consuming and can significantly contribute to the overall costs of the assembly. Moreover, such a procedure is not foolproof in that operator inattention or error may result in an incorrectly positioned assembly. Unfortunately, it is difficult for the orthodontic practitioner to detect whether or not the band and the appliance are correctly assembled. If an improperly assembled assembly is used, the ultimate position or orientation of the tooth or teeth at the conclusion of orthodontic treatment may not be satisfactory and an additional treatment period may be needed.
Clearly, there is a need in the art for an improved means of manufacturing an orthodontic appliance and band assembly. Preferably, such a method would be useful both in the manufacturing plant as well as in the laboratories of orthodontic practitioners who prefer to weld appliances to bands in their offices.